Smoke detectors have been recognized as important safety devices which can be used to provide an early alarm indication in the event that the level of smoke in the ambient atmosphere exceeds a predefined threshold. Both ionization-type and photoelectric-type detectors are known and have been used in both residential and commercial applications.
One aspect of smoke detector-type products is that they do not normally go into an alarm condition and are silent until the level of smoke in the ambient atmosphere exceeds the predetermined value. As a result, the great majority of time the detector is in a non-alarmed state and is not emitting an alarm indication.
Test circuits have, as a result, been developed for the purpose of temporarily placing detectors into an alarmed state to establish whether or not the unit is functioning properly. One such circuit is disclosed in Mallory et al. U.S. Pat. No. 4,321,466.
In battery powered photoelectric detectors where the test circuitry increases the radiant energy output of the light source, the batteries are subjected to an increased current draining during the test interval. It is particularly important in battery powered detectors to minimize current draining so as to maximize long-term battery life.
Hence, it would be desirable to provide test circuitry which does not increase the radiant energy output of the light source of a photoelectric detector, so as to enhance and extend battery life by minimizing current draw while in a test condition.